Evolution chapter 3 flashcards

It states organisms change over generations in the proportions of individual organisms that differ gentically. It is a set of processes (when proportions of individual organisms change genetically over many generations). A theory is a sytem of ideas or statement held as an explanation or account of a group of facts or phenomena.

Microevolution occurs within a species (wisdom teeth) and is small scale, Maceroevolution occurs among species and is large scale (transition from one species to another). Two processes occur within macro and micro evolution, there are processes that create new types of individuals and processes that change the frequency of different type of individuals (mutation - evolved good trait = more of that trait as it is passed on, bad trait = lower frequency of that trait, organisms with trait die)

In the 18th century Georges-Louis Leclerc de Buffon proposed that species could change over time. Carl Linnaeus proposed that species became hybrids that then formed new species. Erasmus Darwin suggested that all life came from a single source. Though there ideas were not widely accepted

He discovered in evolutionary biology, adaptive radiation is a process in which organisms diversify rapidly from an ancestral species into a multitude of new forms, particularly when a change in the enviroment makes new resources availible, creates new challenges, or opens new enviromental niches. He reached his conclusion when he travelled around the world in 1831, he went to the galapagos with endemic species. These species had similar chracteristics, which implied they have common ancestry but were mores suited to survive in their enviroments this shows that adaptive radiation occured from one species and then they evolved to be better suited for their island.

• Observations
• 1. He stated that Individuals within any species exhibit many inherited variations
• 2. Every generation produces far more offspring than can survive to reproduce
• 3. Populations of species tend to remain stable in size

• Inferences
• 1. Individuals of the same species are in a constant struggle for survival (species compete w each other)
• 2. Individuals with more favourable variations are more likely to survive and pass these variations on. Survival is not random - Natural selection (survival of the fittest)
• 3. Since individuals with more favourable variations contribute porportionately more offspring to succeding generations, their favourable inherited variations will become more common.

• 1. There is gentic variation within a population which can be inherited
• 2. Overproduction of offspring leads to competition for survival
• 3. Individuals with beneficial adaptations are more likely to pass on their genes 
• 4. Over many generations there is a change in allele frequency (evolution/selection)

In asexual reproduction all offspring have an exact copy of the single parents DNA. It passes down all its genes and they are usually identical. The only way for variation to happen is through mutations. Examples are stawberries (runners) and bacteria and fission.

In Sexual reproduction the offspring inherit a variation of characteristics, two copies of each gene, one from each parent (50% of dad's genes, 50% of mom's). Sexually reproducing species choose different mates. Offspring are never identical to the parents DNA which causes more variation and the genes that offspring randomly inherit (more genes = more variety) are passed on if they are useful (enviromental selection). If pop. has 1000 males and females there are 1 million diff. mating pairs). Ex: strawberries (seeds).

Usually the DNA of an organism remains the same throughout its life but sometimes random changes can occur called mutations. They can be caused by the enviroment or errors when DNA is replicated. It is the only process that is nessecary and sufficient for evolution. It is a rare occurance which is why evolution can take 100 000's years. It is the only Microevolutionary process that creates new genes. Mutations that help an organism survive are passed on, while lethal that are non beneficial are not passed on. The two types are Somatic/Body cell mutations that cannot be inherited they are caused by the enviroment (skin cancer) and Sex cell mutations which can be inherited and occur in gametes.

Neutral mutations do not have a positive or negative affect on the individual (hair colour variations in siamese cats). Beneficial mutations are the most rare type and hey give the indivdual a competitive advantage. It makes the individual more likely to live, reproduce and pass the gene on. Ex: A mutation that allows humans to survive aids and bacterial resistance. Harmful mutations are more common the mutation results in less fit organisms which makes them less likely to live, reproduce and pass the gene on.

• 1. Mutations do not occur when needed they are random.
• 2. Even though there are more harmful mutations our human DNA won't degrade because the fittest still survive - many babies with mutations do not live to reproduce.
• 3. Even though mutations are chance evolution isn't. Only the best fit mutations pass on, this improves species survival and leads to NATURAL SELECTION.

It is a microevolutionary process that when some individuals have traits (physical, behavioural or physiological) or beneficial mutations that make them better at surviving and reproducing. It is "survival of the fittest" - due to overpopulation only the fittest survive to produce and care for more offspring. Fitness is how well do your traits let you survive, your odds of having children. It is linked to a particular enviroment or habitat - a trait that is advantageous in one enviroment may offer no advantage in another.

After one organism recieves the trait more individuals (offpspring) with that trait will be born. Then the population with the advantageous trait overpopulates and replaces the less fit in the population. Which creates a new population all with the new trait and adapted to their particular enviroment (takes generations). This laeds to adpatation and evolution.